Classifications

• • C—CHEMISTRY; METALLURGY
  • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
  • C08L—COMPOSITIONS OF MACROMOLECULAR COMPOUNDS
  • C08L15/00—Compositions of rubber derivatives
• • C—CHEMISTRY; METALLURGY
  • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
  • C08L—COMPOSITIONS OF MACROMOLECULAR COMPOUNDS
  • C08L25/00—Compositions of, homopolymers or copolymers of compounds having one or more unsaturated aliphatic radicals, each having only one carbon-to-carbon double bond, and at least one being terminated by an aromatic carbocyclic ring; Compositions of derivatives of such polymers
  • C08L25/02—Homopolymers or copolymers of hydrocarbons
  • C08L25/04—Homopolymers or copolymers of styrene
  • C08L25/08—Copolymers of styrene
  • C08L25/10—Copolymers of styrene with conjugated dienes
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B60—VEHICLES IN GENERAL
  • B60C—VEHICLE TYRES; TYRE INFLATION; TYRE CHANGING; CONNECTING VALVES TO INFLATABLE ELASTIC BODIES IN GENERAL; DEVICES OR ARRANGEMENTS RELATED TO TYRES
  • B60C1/00—Tyres characterised by the chemical composition or the physical arrangement or mixture of the composition
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B60—VEHICLES IN GENERAL
  • B60C—VEHICLE TYRES; TYRE INFLATION; TYRE CHANGING; CONNECTING VALVES TO INFLATABLE ELASTIC BODIES IN GENERAL; DEVICES OR ARRANGEMENTS RELATED TO TYRES
  • B60C1/00—Tyres characterised by the chemical composition or the physical arrangement or mixture of the composition
  • B60C1/0016—Compositions of the tread
• • C—CHEMISTRY; METALLURGY
  • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
  • C08C—TREATMENT OR CHEMICAL MODIFICATION OF RUBBERS
  • C08C19/00—Chemical modification of rubber
  • C08C19/20—Incorporating sulfur atoms into the molecule
• • C—CHEMISTRY; METALLURGY
  • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
  • C08K—Use of inorganic or non-macromolecular organic substances as compounding ingredients
  • C08K3/00—Use of inorganic substances as compounding ingredients
  • C08K3/02—Elements
  • C08K3/04—Carbon
• • C—CHEMISTRY; METALLURGY
  • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
  • C08K—Use of inorganic or non-macromolecular organic substances as compounding ingredients
  • C08K3/00—Use of inorganic substances as compounding ingredients
  • C08K3/34—Silicon-containing compounds
  • C08K3/36—Silica
• • C—CHEMISTRY; METALLURGY
  • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
  • C08K—Use of inorganic or non-macromolecular organic substances as compounding ingredients
  • C08K5/00—Use of organic ingredients
  • C08K5/36—Sulfur-, selenium-, or tellurium-containing compounds
  • C08K5/39—Thiocarbamic acids; Derivatives thereof, e.g. dithiocarbamates
  • C08K5/40—Thiurams, i.e. compounds containing groups
• • C—CHEMISTRY; METALLURGY
  • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
  • C08K—Use of inorganic or non-macromolecular organic substances as compounding ingredients
  • C08K9/00—Use of pretreated ingredients
  • C08K9/04—Ingredients treated with organic substances
  • C08K9/06—Ingredients treated with organic substances with silicon-containing compounds
• • C—CHEMISTRY; METALLURGY
  • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
  • C08L—COMPOSITIONS OF MACROMOLECULAR COMPOUNDS
  • C08L19/00—Compositions of rubbers not provided for in groups C08L7/00 - C08L17/00
• • C—CHEMISTRY; METALLURGY
  • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
  • C08K—Use of inorganic or non-macromolecular organic substances as compounding ingredients
  • C08K2201/00—Specific properties of additives
  • C08K2201/002—Physical properties
  • C08K2201/006—Additives being defined by their surface area
• • C—CHEMISTRY; METALLURGY
  • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
  • C08K—Use of inorganic or non-macromolecular organic substances as compounding ingredients
  • C08K5/00—Use of organic ingredients
  • C08K5/54—Silicon-containing compounds
  • C08K5/548—Silicon-containing compounds containing sulfur

Definitions

• This invention relates to a vulcanizable or a vulcanized rubber composition, in particular for a tire or one of its rubber components. Moreover, the present invention is directed to a tire or a rubber component of a tire comprising such a rubber composition.
• a first object of the present invention may be to provide a rubber composition having desirable rolling resistance and/or hysteresis properties.
• Another object of the present invention may be to provide a rubber composition with good stiffness.
• Another object of the present invention may be to provide a rubber composition with limited abrasion.
• Yet another object of the present invention may be to provide a rubber composition exhibiting a good compromise of hysteresis, stiffness and abrasion properties.
• the present invention is directed to a sulfur vulcanizable rubber composition (or alternatively to a vulcanized rubber composition) comprising 50 phr to 100 phr of at least one styrene butadiene rubber functionalized for the coupling to silica, 0 phr to 50 phr of a diene based elastomer, 40 phr to 200 phr of filler, wherein said filler comprises predominantly a silanized or pre-silanized silica.
• the rubber composition comprises at least 0.5 phr of a (sulfur-containing) compound having the structure
• each of R1 to R4 may be an organic group comprising 1 to 20 carbon atoms, wherein each group of R1 to R4 can be different from another group of R1 to R4.
• the inventors have surprisingly found that the combination of polymers functionalized for the coupling to silica together with a silanized or pre-silanized silica and the above compound results in a rubber composition having a good rolling resistance and in addition an unexpectedly high stiffness. While the use of pre-silanized silicas may have resulted in the improvement of rolling resistance in some compositions in the past, stiffness was reduced at the same time. By the combination of features according to the present invention, the latter drawback has unexpectedly been overcome.
• said silanized or pre-silanized silica is a silica which is pre-reacted with a sulfur-containing silane. Pre-reaction with the silane or in other words pre-silanization improves the dispersion of the silica in the rubber composition and is thus technically different from a silanization in the rubber composition.
• the sulfur-containing silane is one or more of i) a bis(3-triethoxysilylpropyl)polysulfide containing an average of from 2 to 5 connecting sulfur atoms in its polysulfidic bridge, and ii) an alkoxyorganomercaptosilane.
• silanes have been found to be the most preferred agents. For example, see U.S. Pat. No. 7,214,731, showing further details of making such pre-silanized silica.
• the amount of mercapto groups on the surface of the silica may be in the range of between 0.1 and 1 weight percent, alternatively 0.4 to 1 weight percent or 0.4 to 0.6 weight percent, wherein 100% represent the whole weight of the silica sample.
• the amount of mercapto groups is measured by titration.
• the silica may comprise a compatibilizer which is typically a (hydro-)carbon chain material having multiple carbon atoms (for instance at least 4 carbon atoms) along its chain.
• a compatibilizer may facilitate the mixing of the composition.
• the weight % of carbon surface load/functionalization is between 2 and 10, or alternatively between 3 and 8. Again, this is based on 100% of the silica sample, by weight.
• the pre-silanized silica has a BET surface area smaller than 150 g/m 2 , preferably smaller than 120 g/m 2 , even more preferably at most 100 g/m 2 .
• the pre-silanized silica has a BET surface area within a range of 50 g/m 2 to 100 g/m 2 .
• a low silica surface area improves dispersion and low hysteresis (but results also in lower stiffness).
• Such a BET surface area is measured herein by Nitrogen adsorption according to ASTM D6556 or equivalent.
• the BET method of measuring surface area is also described, for example, in the Journal of the American Chemical Society, Volume 60.
• the pre-silanized (and optionally precipitated) silica has a CTAB adsorption surface area of between 130 m 2 /g and 210 m 2 /g, optionally between 130 m 2 /g and 150 m 2 /g.
• CTAB cetyl trimethyl ammonium bromide
• the pre-silanized silica may optionally be treated with a silica dispersing aid.
• silica dispersing aids may include glycols, such as fatty acids, diethylene glycols, polyethylene glycols, fatty acid esters of hydrogenated or non-hydrogenated C 5 or C 6 sugars, and polyoxyethylene derivatives of fatty acid esters of hydrogenated or non-hydrogenated C 5 or C 6 sugars.
• Exemplary fatty acids include stearic acid, palmitic acid and oleic acid.
• Exemplary fatty acid esters of hydrogenated and non-hydrogenated C 5 and C 6 sugars include, but are not limited to, the sorbitan oleates, such as sorbitan monooleate, dioleate, trioleate and sesquioleate, as well as sorbitan esters of laurate, palmitate and stearate fatty acids.
• Exemplary polyoxyethylene derivatives of fatty acid esters of hydrogenated and non-hydrogenated C 5 and C 6 sugars include, but are not limited to, polysorbates and polyoxyethylene sorbitan esters, which are analogous to the fatty acid esters of hydrogenated and non-hydrogenated sugars noted above except that ethylene oxide groups are placed on each of the hydroxyl groups.
• the optional silica dispersing aids are present in an amount ranging from 0.1% to 25% by weight based on the weight of the silica, with 0.5% to 20% by weight being suitable, and 1% to 15% by weight based on the weight of the silica also being suitable.
• the pre-silanized silica is pre-hydrophobated by treating silica in an aqueous colloidal form thereof with both an organomercaptosilane and an alkylsilane in a weight ratio of said organomercaptosilane to said alkylsilane in a range of from 10/90 to 90/10; wherein said alkylsilane is of the general Formula (I):
• R is an alkyl radical having from 1 to 18 carbon atoms, preferably from 1 to 8 carbon atoms, such as, methyl, ethyl, isopropyl, n-butyl and octadecyl radicals
• n is a numeral from 1 to 3
• X is a radical selected from halogens, namely chlorine or bromine, preferably a chlorine radical, and alkoxy radicals, preferably an alkoxy radical as (R 1 O)—, wherein R 1 is an alkyl radical having from 1 to 3 carbon atoms, such as, methyl, ethyl and isopropyl radicals, preferably from methyl and ethyl radicals, and where said organomercaptosilane is of the general formula (II):
• X is a radical selected from halogens, such as chlorine or bromine, preferably a chlorine radical, and alkyl radicals having from 1 to 16 carbon atoms, preferably selected from methyl, ethyl, n-propyl, and n-butyl radicals; wherein R 2 is an alkyl radical having from 1 to 16 carbon atom, preferably from 1 to 4 carbon atoms, preferably selected from methyl and ethyl radicals and R 3 is an alkylene radical having from 1 to 16 carbon atoms, preferably from 1 to 4 carbon atoms, preferably a propylene radical; wherein n represents an integer from 0 to 3 with n preferably representing zero.
• halogens such as chlorine or bromine, preferably a chlorine radical
• alkyl radicals having from 1 to 16 carbon atoms, preferably selected from methyl, ethyl, n-propyl, and n-butyl radicals
• R 2 is an alkyl radical having from 1
• Representative alkylsilanes of Formula (I) are, for example, trichloro methyl silane, dichloro dimethyl silane, chloro trimethyl silane, trimethoxy methyl silane, dimethoxy dimethyl silane, methoxy trimethyl silane, trimethoxy propyl silane, trimethoxy octyl silane, trimethoxy hexadecyl silane, dimethoxy dipropyl silane, triethoxy methyl silane, triethoxy propyl silane, triethoxy octyl silane, and diethoxy dimethyl silane.
• Organomercaptosilanes of Formula (II) are, for example, triethoxy mercaptopropyl silane, trimethoxy mercaptopropyl silane, methyl dimethoxy mercaptopropyl silane, methyl diethoxy mercaptopropyl silane, dimethyl methoxy mercaptopropyl silane, triethoxy mercaptoethyl silane, and tripropoxy mercaptopropyl silane.
• pre-silanized silicas which are suitable for use in the practice of this invention include, but are not limited to, Ciptane® 255 LD and Ciptane® LP (PPG Industries) silicas that have been pre-treated with a mercaptosilane, and Coupsil® 8113 (Degussa) that is the product of the reaction between organosilane Bis(triethoxysilylpropyl) polysulfide (Si69) and Ultrasil® VN3 silica, and Coupsil® 6508, Agilon® 400 silica from PPG Industries, Agilon® 454 silica from PPG Industries, and Agilon® 458 silica from PPG Industries.
• the rubber composition is exclusive of non-pre-silanized silica or comprises less than 10 phr, preferably less than 5 phr of non-pre-silanized silica.
• the pre-silanized silica is not necessarily pre-silanized precipitated silica herein but is preferably pre-silanized precipitated silica.
• the rubber composition may also include (non-pre-silanized/conventional) silica which is optionally precipitated silica.
• its BET surface area may be in the range of 40 to 600 square meters per gram.
• the BET surface area may be in a range of 80 to 300 square meters per gram.
• the conventional silica may also be characterized by having a dibutylphthalate (DBP) absorption value in a range of 100 to 400, alternatively 150 to 300.
• DBP dibutylphthalate
• a conventional silica might be expected to have an average ultimate particle size, for example, in the range of 0.01 to 0.05 micron as determined by the electron microscope, although the silica particles may be even smaller, or possibly larger, in size.
• silicas such as, only for example herein, and without limitation, silicas commercially available from PPG Industries under the Hi-Sil trademark with designations 210, 315G, EZ160G, etc; silicas available from Solvay, with, for example, designations of Z1165MP and Premium200MP, etc.; and silicas available from Evonik AG with, for example, designations VN2 and Ultrasil 6000GR, 9100GR, etc.
• the rubber composition contains conventional/non-pre-silanized silica (in addition to said pre-silanized silica)
• said rubber composition contains added silica coupler (silica coupler added to said rubber composition), wherein said silica coupler has a moiety reactive with hydroxyl groups (e.g. silanol groups) on said silica and said pre-silanized silica and another different moiety interactive with the elastomers of the rubber composition.
• said silica coupler added to said rubber composition is comprised of bis(3-triethoxysilylpropyl) polysulfide having an average of from 2 to 4 connecting sulfur atoms in its polysulfidic bridge.
• silica coupler having a moiety reactive with hydroxyl groups on pre-silanized silica and on silica and another moiety interactive with said elastomers, may be comprised of, for example:
• a representative of such bis(3-trialkoxysilylalkyl) polysulfide is comprised of bis(3-triethoxysilylpropyl) polysulfide.
• the silica coupler may be desirably an alkoxyorganomercaptosilane.
• the silica coupler may be desirably comprised of the bis(3-triethoxysilylpropyl) polysulfide.
• the rubber composition may contain a conventional sulfur containing organosilicon compounds or silanes.
• suitable sulfur containing organosilicon compounds are of the formula:
• R 1 is an alkyl group of 1 to 4 carbon atoms, cyclohexyl or phenyl;
• R 2 is an alkoxy of 1 to 8 carbon atoms, or cycloalkoxy of 5 to 8 carbon atoms;
• Alk is a divalent hydrocarbon of 1 to 18 carbon atoms and n is an integer of 2 to 8.
• the sulfur containing organosilicon compounds are the 3,3′-bis(trimethoxy or triethoxy silylpropyl) polysulfides.
• the sulfur containing organosilicon compounds are 3,3′-bis(triethoxysilylpropyl) disulfide and/or 3,3′-bis(triethoxysilylpropyl) tetrasulfide. Therefore, as to formula I, Z may be
• suitable sulfur containing organosilicon compounds include compounds disclosed in U.S. Pat. No. 6,608,125.
• the sulfur containing organosilicon compounds includes 3-(octanoylthio)-1-propyltriethoxysilane, CH 3 (CH 2 ) 6 C( ⁇ O)—S—CH 2 CH 2 CH 2 Si(OCH 2 CH 3 ) 3 , which is available commercially as NXTTM from Momentive Performance Materials.
• suitable sulfur containing organosilicon compounds include those disclosed in United States Patent Publication No. 2003/0130535.
• the sulfur containing organosilicon compound is Si-363 from Degussa.
• the amount of the sulfur containing organosilicon compound in a rubber composition may vary depending on the level of other additives that are used. Generally speaking, the amount of the compound may range from 0.5 phr to 20 phr. In one embodiment, the amount will range from 1 phr to 10 phr.
• the rubber composition is exclusive of a separate silica coupler, i.e. a silica coupler added separately to the rubber composition.
• said filler comprises at least 50 phr of silica, preferably from 50 phr to 160 phr of silica, wherein the silica comprises predominantly pre-silanized silica (all by weight) or consists of pre-silanized silica.
• said filler comprises from 45 phr of the pre-silanized silica to 150 phr of the pre-silanized silica, preferably from 60 phr to 150 phr such as for passenger car tire (tread) applications.
• said filler comprises from 25 phr to 60 phr of the pre-silanized silica. Such a range has been found to be of particular interest for truck tire (tread) applications.
• the filler comprises from 50 phr to 150 phr (preferably from 50 phr to 100 phr, or even more preferably from 50 phr to 85 phr) of the pre-silanized silica.
• the present invention could be of interest for moderately filled rubber compositions.
• the filler comprises less than 10 phr of carbon black. Such a relatively low carbon black content is deemed desirable to further improve hysteresis properties.
• said filler comprises less than 25 phr of carbon black, preferably less than 10 phr of carbon black, or even more preferably less than 5 phr of carbon black.
• the rubber composition comprises at most 10 phr of liquid plasticizers, preferably at most 7 phr of liquid plasticizers.
• liquid plasticizers A limited amount of liquid plasticizers has been found to be preferable by the inventors.
• Liquid plasticizer means herein a plasticizer which is in a liquid state at 23° C.
• the rubber composition comprises less than 10 phr of oil, preferably less than 7 phr of oil. It may also comprise at most 5 phr of oil or be essentially or entirely free of oil.
• the rubber composition comprises from 0.5 phr to 5 phr (preferably from 1 phr to 4 phr, or even more preferably from 1 phr to 2.5 phr) of the sulfur-containing compound.
• An even more preferred range is 1 phr to 2 phr, or most preferably 1 phr to 1.7 phr of the sulfur-containing compound.
• Already relatively small amounts may be sufficient to obtain the desired effect.
• one or more of R1, R2, R3, R4 comprise (or consist of) a cyclic, e.g. a benzyl group.
• said sulfur-containing compound has the following structure:
• said sulfur-containing compound is an 1,6-bis(N,N-dibenzylthiocarbamoyldithio)alkane, preferably 1,6-bis(N,N-dibenzylthiocarbamoyldithio)hexane.
• the rubber composition comprises at least 5 phr of a hydrocarbon resin, preferably a plasticizing hydrocarbon resin.
• said resin is chosen from the list of coumarone-indene-resins, petroleum resins, (aliphatic) C5 resins, (aromatic) C9 resins, C5/C9 resins, DCPD resins, CPD resins, MCPD resins, terpene resins, alphamethyl styrene resins, and combinations of those.
• such resins could also be functionalized and/or at least partially hydrogenated.
• a glass transition temperature of the resin is within a range of 30° C. to 80° C., preferably 40° C. to 80° C.
• a glass transition temperature of a resin is determined herein as a peak midpoint by a differential scanning calorimeter (DSC) at a temperature rate of increase of 10° C. per minute, according to ASTM D6604 or equivalent.
• the resin has a softening point of at least 95° C. as determined according to ASTM E28, or equivalent, which might sometimes be referred to as a ring and ball softening point.
• the softening point is at most 140° C. or more preferably at most 120° C.
• the resin has an average molecular weight Mw within a range of 150 g/mol to 3000 g/mol, preferably 500 g/mol to 2500 g/mol. Mw is determined with gel permeation chromatography (GPC) using polystyrene calibration standards according to ASTM 5296-11 or equivalent.
• the styrene butadiene rubber has one or more of: i) a styrene content of less than 40% (and preferably more than 5%), and ii) a vinyl content within a range of 30% to 60% (preferably 35% to 55%), iii) a glass transition temperature within a range of ⁇ 10° C. to ⁇ 40° C. (preferably ⁇ 15° C. to ⁇ 35° C.).
• the relatively high glass transition temperature range can for instance be of particular interest in polymer blends with other low glass transition temperature polymers to obtain a relatively high rubber compound glass transition temperature.
• the styrene butadiene rubber is a solution-polymerized styrene butadiene rubber. This is the preferred styrene butadiene rubber used herein.
• the rubber composition comprises less than 0.9 phr of sulfur (or, in other words, elemental sulfur, which is for instance added as pure sulfur to the rubber composition), preferably less than 0.7 phr of sulfur.
• the rubber composition comprises more than 0.2 phr of sulfur, or even more preferably more than 0.3 phr of sulfur. In particular, this is desirable in combination with the sulfur containing compound according to the present invention.
• elemental sulfur or pure sulfur shall be understood herein as sulfur which is not bound in a silane or an accelerator.
• the styrene butadiene rubber has a weight average molecular weight (Mw) within a range of 200,000 g/mol to 500,000 g/mol. Lower molecular weights are less desirable as those may increase hysteresis. Higher molecular weights are less desirable as they limit processability.
• a weight average molecular weight Mw is determined using gel permeation chromatography (GPC) according to ASTM 5296-11 using polystyrene calibration standards.
• the styrene butadiene rubber functionalized for the coupling to silica has at least one amino group, preferably at least one amino silane or at least one amino siloxane group.
• the styrene butadiene rubber functionalized for the coupling to silica has at least at 85% (preferably at 90%) of its chain ends at least one functional group, preferably at least one of the groups as mentioned herein above.
• the rubber composition comprises 70 phr to 100 phr of the styrene butadiene rubber, and 0 phr to 30 phr of one or more of polybutadiene rubber, polyisoprene, and natural rubber.
• the rubber composition comprises 70 phr to 100 phr of two styrene butadiene rubbers functionalized for the coupling to silica and 0 phr to 30 phr of one or more of polybutadiene rubber, polyisoprene, and natural rubber.
• the two styrene butadiene rubbers could have different glass transition temperatures such as below ⁇ 50° C. and above ⁇ 50° C.
• the rubber composition further comprises at least 0.2 phr of vulcanizing agents, preferably comprising elemental sulfur.
• the composition may comprise from 0.4 phr to 15 phr of vulcanizing agents which may comprise, but are not limited to, elemental sulfur or sulfur containing silanes.
• the rubber composition may include at least one and/or one additional diene-based rubber.
• Representative synthetic polymers may be the homopolymerization products of butadiene and its homologues and derivatives, for example, methylbutadiene, dimethylbutadiene and pentadiene as well as copolymers such as those formed from butadiene or its homologues or derivatives with other unsaturated monomers.
• acetylenes for example, vinyl acetylene
• olefins for example, isobutylene, which copolymerizes with isoprene to form butyl rubber
• vinyl compounds for example, acrylic acid, acrylonitrile (which polymerize with butadiene to form NBR), methacrylic acid and styrene, the latter compound polymerizing with butadiene to form SBR, as well as vinyl esters and various unsaturated aldehydes, ketones and ethers, e.g. acrolein, methyl isopropenyl ketone and vinylethyl ether.
• synthetic rubbers include neoprene (polychloroprene), polybutadiene (including cis 1,4-polybutadiene), polyisoprene (including cis 1,4-polyisoprene), butyl rubber, halobutyl rubber such as chlorobutyl rubber or bromobutyl rubber, styrene/isoprene/butadiene rubber, copolymers of 1,3-butadiene or isoprene with monomers such as styrene, acrylonitrile and methyl methacrylate, as well as ethylene/propylene terpolymers, also known as ethylene/propylene/diene monomer (EPDM), and in particular, ethylene/propylene/dicyclopentadiene terpolymers.
• neoprene polychloroprene
• polybutadiene including cis 1,4-polybutadiene
• Rubbers which may be used include alkoxy-silyl end functionalized solution polymerized polymers (SBR, PBR, IBR and SIBR), silicon-coupled and tin-coupled star-branched polymers.
• SBR alkoxy-silyl end functionalized solution polymerized polymers
• PBR polybutadiene
• SIBR silicon-coupled star-branched polymers.
• Preferred rubber or elastomers may be in general natural rubber, synthetic polyisoprene, polybutadiene and SBR including SSBR.
• One or more of these rubbers may be functionalized, such as for the coupling to silica.
• the composition may comprise at least two diene-based rubbers.
• a combination of two or more rubbers is preferred such as cis 1,4-polyisoprene rubber (natural or synthetic, although natural is preferred), 3,4-polyisoprene rubber, styrene/isoprene/butadiene rubber, emulsion and solution polymerization derived styrene/butadiene rubbers, cis 1,4-polybutadiene rubbers and emulsion polymerization prepared butadiene/acrylonitrile copolymers.
• the partially saturated elastomer may also be a diene-based polymer but it is not necessarily diene-based.
• an emulsion polymerization derived styrene/butadiene might be used having a styrene content of 20 to 35 percent bound styrene or, for some applications, an ESBR having a medium to relatively high bound styrene content, namely a bound styrene content of 30 to 45 percent.
• ESBR emulsion polymerization prepared ESBR, it may be meant that styrene and 1,3-butadiene are copolymerized as an aqueous emulsion. Such are well known to those skilled in such art.
• the bound styrene content can vary, for example, from 5 to 50 percent.
• the ESBR may also contain acrylonitrile to form a terpolymer rubber, as ESBR, in amounts, for example, of 2 to 30 weight percent bound acrylonitrile in the terpolymer.
• ESBR acrylonitrile to form a terpolymer rubber
• Emulsion polymerization prepared styrene/butadiene/acrylonitrile copolymer rubbers containing 2 to 40 weight percent bound acrylonitrile in the copolymer may also be contemplated as diene-based rubbers.
• solution polymerization prepared styrene butadiene rubber may be used.
• SSBR styrene butadiene rubber
• Such an SSBR may for instance have a bound styrene content in a range of 5 to 50 percent, preferably 9 to 36, percent.
• the SSBR can be conveniently prepared, for example, by anionic polymerization in an inert organic solvent. More specifically, the SSBR can be synthesized by copolymerizing styrene and 1,3-butadiene monomer in a hydrocarbon solvent utilizing an organo lithium compound as the initiator. As noted above, such a rubber may also be functionalized for the coupling to silica.
• a synthetic or natural polyisoprene rubber may be used.
• Synthetic cis 1,4-polyisoprene and cis 1,4-polyisoprene natural rubber are as such well known to those having skill in the rubber art.
• the cis 1,4-content may be at least 90%, optionally at least 95%.
• cis 1,4-polybutadiene rubber (BR or PBD) is used.
• Suitable polybutadiene rubbers may be prepared, for example, by organic solution polymerization of 1,3-butadiene.
• the BR may be conveniently characterized, for example, by having at least a 90 percent cis 1,4-content (“high cis” content) and a glass transition temperature Tg in a range of from ⁇ 95° C. to ⁇ 110° C.
• Suitable polybutadiene rubbers are available commercially, such as Budene® 1207, Budene® 1208, Budene® 1223, or Budene® 1280 from The Goodyear Tire & Rubber Company.
• These high cis-1,4-polybutadiene rubbers can for instance be synthesized utilizing nickel catalyst systems which include a mixture of (1) an organonickel compound, (2) an organoaluminum compound, and (3) a fluorine containing compound as described in U.S. Pat. Nos. 5,698,643 and 5,451,646.
• a glass transition temperature, or Tg, of an elastomer or rubber represents the glass transition temperature(s) of the respective elastomer or rubber in its uncured state.
• a glass transition temperature, or Tg, of an elastomer composition or a rubber composition represents the glass transition temperatures of the respective elastomer composition or rubber composition in its cured state.
• a Tg is determined as a peak midpoint by a differential scanning calorimeter (DSC) at a temperature rate of increase of 10° C. per minute, according to ASTM D3418.
• DSC differential scanning calorimeter
• phr refers to “parts by weight of a respective material per 100 parts by weight of rubber, or elastomer”.
• an rubber composition is comprised of 100 parts by weight of rubber/elastomer.
• the claimed composition may comprise other rubbers/elastomers than explicitly mentioned in the claims, provided that the phr value of the claimed rubbers/elastomers is in accordance with claimed phr ranges and the amount of all rubbers/elastomers in the composition results in total in 100 parts of rubber.
• the composition may further comprise from 1 phr to 10 phr, optionally from 1 phr to 5 phr, of one or more additional diene-based rubbers, such as SBR, SSBR, ESBR, PBD/BR, NR and/or synthetic polyisoprene.
• the composition may include less than 5, preferably less than 3, phr of an additional diene-based rubber or be also essentially free of such an additional diene-based rubber.
• the terms “rubber” and “elastomer” may be used herein interchangeably, unless indicated otherwise.
• the rubber composition may also include oil, in particular processing oil.
• Processing oil may be included in the rubber composition as extending oil typically used to extend elastomers. Processing oil may also be included in the rubber composition by addition of the oil directly during rubber compounding. The processing oil used may include both extending oil present in the elastomers, and process oil added during compounding.
• Suitable process oils may include various oils as are known in the art, including aromatic, paraffinic, naphthenic, vegetable oils, and low PCA oils, such as MES, TDAE, SRAE and heavy naphthenic oils.
• Suitable low PCA oils may include those having a polycyclic aromatic content of less than 3 percent by weight as determined by the IP346 method. Procedures for the IP346 method may be found in Standard Methods for Analysis & Testing of Petroleum and Related Products and British Standard 2000 Parts, 2003, 62nd edition, published by the Institute of Petroleum, United Kingdom.
• the rubber composition may include also carbon black as one of the filler materials.
• Preferred amounts in this application range from 0.5 phr to 25 phr, preferably from 0.5 phr to 10 phr or from 0.5 phr to 5 phr.
• carbon blacks include N110, N121, N134, N220, N231, N234, N242, N293, N299, N315, N326, N330, N332, N339, N343, N347, N351, N358, N375, N539, N550, N582, N630, N642, N650, N683, N754, N762, N765, N774, N787, N907, N908, N990 and N991 grades. These carbon blacks have iodine absorptions ranging from 9 g/kg to 145 g/kg and a DBP number ranging from 34 cm 3 /100 g to 150 cm 3 /100 g.
• other fillers may be used in the rubber composition including, but not limited to, particulate fillers including ultra-high molecular weight polyethylene (UHMWPE), crosslinked particulate polymer gels including but not limited to those disclosed in U.S. Pat. Nos. 6,242,534, 6,207,757, 6,133,364, 6,372,857, 5,395,891 or U.S. Pat. No. 6,127,488, and a plasticized starch composite filler including but not limited to that disclosed in U.S. Pat. No. 5,672,639.
• Such other fillers may be used in an amount ranging from 1 phr to 10 phr.
• the rubber composition may be compounded by methods generally known in the rubber compounding art, such as mixing the various sulfur-vulcanizable constituent rubbers with various commonly used additive materials such as, for example, sulfur donors, curing aids, such as activators and retarders, and processing additives, such as oils, resins including tackifying resins and plasticizers, fillers, pigments, fatty acid, zinc oxide, waxes, antioxidants and antiozonants and peptizing agents.
• additives mentioned above are selected and commonly used in conventional amounts.
• sulfur donors include elemental sulfur (free sulfur), an amine disulfide, polymeric polysulfide and sulfur olefin adducts.
• the sulfur-vulcanizing agent is elemental sulfur.
• the sulfur-vulcanizing agent may for instance be used in an amount ranging from 0.5 phr to 8 phr, alternatively within a range of from 1.5 phr to 6 phr.
• Typical amounts of tackifier resins, if used, comprise for example 0.5 phr to 10 phr, usually 1 phr to 5 phr.
• processing aids if used, comprise for example 1 phr to 50 phr (this may comprise in particular oil).
• Typical amounts of antioxidants may for example comprise 1 phr to 5 phr.
• Representative antioxidants may be, for example, diphenyl-p-phenylenediamine and others, such as, for example, those disclosed in The Vanderbilt Rubber Handbook (1978), Pages 344 through 346.
• Typical amounts of antiozonants, if used may for instance comprise 1 phr to 5 phr.
• Typical amounts of fatty acids, if used, which can include stearic acid may for instance comprise 0.5 phr to 3 phr.
• Typical amounts of waxes if used, may for example comprise 1 phr to 5 phr. Often microcrystalline waxes are used.
• Typical amounts of peptizers may for instance comprise 0.1 phr to 1 phr.
• Typical peptizers may be, for example, pentachlorothiophenol and dibenzamidodiphenyl disulfide.
• Accelerators may be preferably but not necessarily used to control the time and/or temperature required for vulcanization and to improve the properties of the vulcanizate.
• a single accelerator system may be used, i.e. primary accelerator.
• the primary accelerator(s) may be used in total amounts ranging from 0.5 phr to 4 phr, alternatively 0.8 phr to 1.5 phr.
• combinations of a primary and a secondary accelerator might be used with the secondary accelerator being used in smaller amounts, such as from 0.05 phr to 3 phr, in order to activate and to improve the properties of the vulcanizate.
• accelerators might be expected to produce a synergistic effect on the final properties and are somewhat better than those produced by use of either accelerator alone.
• delayed action accelerators may be used which are not affected by normal processing temperatures but produce a satisfactory cure at ordinary vulcanization temperatures.
• Vulcanization retarders might also be used.
• Suitable types of accelerators that may be used in the present invention are for instance amines, disulfides, guanidines, thioureas, thiazoles, thiurams, sulfenamides, dithiocarbamates and xanthates.
• the primary accelerator is a sulfenamide.
• the secondary accelerator may be for instance a guanidine, dithiocarbamate or thiuram compound.
• Suitable guanidines include dipheynylguanidine and the like.
• Suitable thiurams include tetramethylthiuram disulfide, tetraethylthiuram disulfide, and tetrabenzylthiuram disulfide.
• the mixing of the rubber composition can be accomplished by methods known to those having skill in the rubber mixing art.
• the ingredients may be typically mixed in at least two stages, namely, at least one nonproductive stage followed by a productive mix stage.
• the final curatives including sulfur-vulcanizing agents may be typically mixed in the final stage which is conventionally called the “productive” mix stage in which the mixing typically occurs at a temperature, or ultimate temperature, lower than the mix temperature(s) of the preceding nonproductive mix stage(s).
• the terms “nonproductive” and “productive” mix stages are well known to those having skill in the rubber mixing art.
• the rubber composition may be subjected to a thermomechanical mixing step.
• the thermomechanical mixing step generally comprises a mechanical working in a mixer or extruder for a period of time, for example suitable to produce a rubber temperature which is within the range of 140° C. to 190° C.
• the appropriate duration of the thermomechanical working varies as a function of the operating conditions, and the volume and nature of the components.
• the thermomechanical working may be from 1 to 20 minutes.
• a vulcanized rubber composition is provided, which is based on the rubber composition according to the first aspect of the present invention.
• the vulcanized rubber composition is the vulcanization product of the sulfur vulcanizable rubber composition according to the first aspect of the invention and/or one or more of its embodiments.
• a rubber component preferably a rubber component for a tire, is provided, in particular comprising the rubber composition in accordance with the first aspect of the invention, or in accordance with the second aspect of the invention, and/or one or more of their embodiments.
• the tire may be an uncured tire or cured, i.e. a vulcanized, tire.
• a tire comprising the rubber composition according to the first aspect or second aspect of the invention, or has a rubber component according to the third aspect of the invention.
• the tire comprises a tread, preferably a tread cap, comprising the rubber composition.
• the tire has a radially outer tread cap layer, intended to come into contact with the road when driving, comprising the rubber composition.
• the tire of the present invention may for example be a pneumatic tire or nonpneumatic tire, a race tire, a passenger tire, an aircraft tire, an agricultural tire, an earthmover tire, an off-the-road (OTR) tire, a truck tire or a motorcycle tire.
• the tire may also be a radial or bias tire.
• Vulcanization of the pneumatic tire may for instance be carried out at conventional temperatures which is within the range of 100° C. to 200° C. In one embodiment, the vulcanization is conducted at temperatures which are within the range of 110° C. to 180° C. Any of the usual vulcanization processes may be used such as heating in a press or mold, heating with superheated steam or hot air. Such tires can be built, shaped, molded and cured by various methods which are known and will be readily apparent to those having skill in such art.
• the present invention is directed to a method of making a rubber composition (e.g., the rubber composition as described in the aforementioned aspects), the method comprising one or more of the following steps:
• the present invention is directed to a method of manufacturing a tire, preferably with the composition according to an aforementioned aspect and/or made with the method of making the rubber composition according to the fifth aspect, wherein the method of manufacturing the tire comprises:
• Comparative Example 1 shows a rubber composition which comprises the same diene-based rubber matrix as Comparative Example 2. Most ingredients of both compositions are the same. However, Comparative Example 1 has 80 phr of conventional silica together with 7 phr of added Silane 1, whereas Comparative Example 2 has 90 phr of pre-silanized silica. Moreover, Comparative Example 1 comprises 10 phr of oil whereas Comparative Example 2 comprises 5 phr of oil. For example, these two Comparative Examples show that typically the use of pre-silanized silica instead of comparable amounts of conventional, i.e. non-pre-silanized silica decreases the compound stiffness as further shown herein in below Table 2.
• Example 2 SSBR 1 1 80 80 PBD 1 2 20 20 Resin 1 3 7 7 Waxes 1.5 1.5 Oil 4 10 5 Processing aids 5 3 3 Stearic Acid 3 3 Silica 6 80 0 Pre-silanized silica 7 0 90 Silane 1 8 7 0 Zinc Oxide 2.5 2.5 Sulfur 1.3 1.3 Antidegradants 9 3 3 DPG 10 2.9 0 CBS 11 2.3 2.3 Silane 2 on carbon black carrier 12 2 2 1 Solution polymerized styrene butadiene rubber as SLR-4602 from Trinseo 2 Polybutadiene rubber as Budene TM 1223 from Goodyear 3 Polyterpene resin as Sylvatraxx TM 4150 from Arizona Chemical 4 TDAE oil 5 including glycerine monoesters of stearic acid and zinc soaps of fatty acids 6 Precipitated silica as Zeosil TM Premium 200MP from Solvay 7 Pre-silanized, precipitated
• Comparative Example 2 is considerably smaller than the stiffness of Comparative Example 1 as shown by the about 35% drop in stiffness. That drop is even more remarkable as the composition of Comparative Example 2 has already an increased content of silica, wherein more filler typically also increases the stiffness of the composition. Even more, Comparative Example 2 has 5 phr less oil than Comparative Example 1 which typically also increases the compound stiffness. According to a non-binding theory of the inventors, the pre-silanized silica may disperse better in the rubber composition which could result in a reduced stiffness.
• Tangent Delta is improved by the use of the pre-silanized silica by about 14%.
• Tangent Delta can be considered as a hysteresis indicator so that its reduction indicates a reduced hysteresis and thus rolling resistance if the rubber composition is used in a tire. While the above-described improvement in Tangent Delta is desirable, the significant drop in stiffness may for instance be undesirable from many performance oriented tire applications.
• Table 3 comprises further Comparative Examples, which are not in accordance with the present invention, as well as Inventive Examples 1 and 2, which are embodiments in accordance with the present invention. All Examples of Table 3 comprise solution-polymerized styrene-butadiene rubbers which are functionalized for the coupling to silica together with a polybutadiene rubber. Moreover, Comparative Example 4, Inventive Example 1 and Inventive Example 2 comprise pre-silanized silica, whereas Comparative Example 3 comprises conventional silica. Both Inventive Examples comprise further a sulfur-containing compound of the structure
• Inventive Example 1 comprises a smaller amount of the compound and Inventive Example 2 comprises a larger amount.
• All Examples of Table 3 comprise a plasticizing resin.
• Example 4 Example 1 Example 2 SSBR 2 13 or SSBR 3 14 80 80 80 80 PBD 1 2 20 20 20 20 20 Resin 1 3 7 7 7 7 Waxes 1.5 1.5 1.5 1.5 Oil 4 10 5 5 5 Stearic Acid 3 3 1 1 Silica 6 80 0 0 0 Pre-silanized silica 7 0 90 90 90 Silane 1 8 7 0 0 0 Zinc Oxide 2.5 2.5 1 1 Processing aids 5 3 3 2 3 Sulfur 1.2 1.2 0.55 0.55 Antidegradants 9 3 5.2 5.2 5.2 DPG 10 2.9 0 0 0 CBS 11 2.3 2.3 1.3 1.5 Sulfur-containing 0 0 1.4 1.7 compound 15 Silane 2 on carbon black 2 2 2 2 carrier 12 13 Solution polymerized styrene butadiene rubber functionalized for the coupling to silica having a glass transition temperature of ⁇ 25° C., a bound styrene butadiene rubber functionalized for the coupling to silica having a glass transition temperature of ⁇
• Table 5 shows similar measurements as Table 4 but considering SSBR 3 instead of the same compositions with SSBR 2.

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